In some combustion engines, such as engines combusting gasoline, diesel, natural gas, propane, methane, other gaseous hydrocarbons and the like, a fuel air mixture is produced upstream from a turbo compressor and fed into the turbo compressor to increase the fluid pressure prior to injection into a combustion chamber. The fuel is mixed with air, typically after the air passes through an air filter, in a fuel air mixing tube a short distance away from an inlet of the turbo compressor. If the fuel and air are not fully mixed prior to entering the turbo compressor, the fuel air mixture can have variable densities and temperatures when the mixture comes into contact with the blades of the turbo compressor that are moving at a high rate of speed.
FIG. 1 illustrates an example of a fuel air mixing tube 10 that is presently used in combustion engines. The exemplary fuel air mixing tube 10 includes a mixing elbow 12 having an inlet 14 that receives air from an air filter (not shown) of the combustion engine and an outlet 16 that outputs the fuel air mixture to a turbo compressor (not shown) of the engine. An end of a fuel tube 18 is inserted through an opening 20 through the external surface of the mixing elbow 12 and into the interior of the mixing elbow 12 to position the fuel tube 18 in the flow path of the air from the air filter. The fuel tube 18 includes one or more orifices 22 positioned at the end of the fuel tube 18 disposed within the interior of the mixing elbow 12. Gaseous fuel from a fuel source (not shown) of the gaseous fuel combustion engine is pumped from a regulator (not shown) through the field tube 18 and exits the field tube 18 through the orifices 22 and into the interior of the mixing elbow 12. The fuel exiting the orifices 22 mixes with the air from the air filter to produce the fuel air mixture that is discharged from the outlet 16 to the turbo compressor.
In the arrangement of the fuel air mixing tube 10 shown in FIG. 1, the gaseous fuel and the air are not well mixed when the fuel air mixture is discharged from the outlet 16 of the mixing elbow 12 and arrives at the turbo compressor. The poor mixing results in variable densities and temperatures in the fuel air mixture instead of a consistent mixture passing through the turbo compressor. FIG. 2 illustrates the mixture of fuel and air that is produced at the outlet 16 of the mixing elbow 12. After the injection of fuel through the orifices 22, a central strip 24 having a high concentration cloud of fuel is formed at the center of the outlet 16, and lateral areas 26 having relatively low concentrations of fuel and high concentrations of air are formed on either side of the central strip 24. When this non-uniformly distributed mixture comes into contact with the turbine blades, impact of the higher density mixture of the central strip 24 on the turbine blades can fatigue the turbine blades over time at a relatively rapid rate. The turbo compressor wheels spin at a high rate of speed, and the high density portion of the fuel air mixture can cause fatigue cycles in minutes to hours that lead to premature failures of the turbine blades. In view of the risk of premature failure of the turbine blades caused by the fuel air mixture produced by the existing fuel air mixing tube 10, a need exists for an improved fuel air mixer providing a more optimal fuel air mixture with more uniform densities and temperatures that does not unduly increase the rate of accumulation of fatigue on the turbine blades.